Worked example: two_led_thermo

A minimal cuewire rig in two LEDs, one thermistor, and a camera TTL trigger. Walks a 105-second phasing protocol while streaming 10 Hz CSV telemetry to a log file.

Hardware

Function	Pin	Notes
LED A	D9	series resistor (220 Ω) to GND
LED B	D10	series resistor to GND
Camera TTL	D11	HIGH = recording
NTC thermistor	A0	5 V — 10 kΩ — A0 — NTC — GND

The thermistor branch matches a 10 kΩ-at-25 °C, β-3950 NTC bead; adjust THERM_R25 and THERM_BETA in thermistor.ino for other parts.

Protocol

Nine integer commands plus the 1337 handshake:

Method	Integer	Effect
rig.comm_test_minimal()	1337	50 1337 echo
rig.write_out(True)	100	start 10 Hz telemetry
rig.write_out(False)	101	stop telemetry
rig.led_a(True)	200	LED A on
rig.led_a(False)	201	LED A off
rig.led_b(True)	210	LED B on
rig.led_b(False)	211	LED B off
rig.camera(True)	300	camera TTL HIGH
rig.camera(False)	301	camera TTL LOW

Telemetry frame, one CSV line every 100 ms:

>clock_s,temp_C,led_a,led_b,cam<

Phase machine

run_protocol() walks five phases (105 s total):

camera ON
├── 30 s   PRE_STIM     both LEDs off
├── 15 s   LIGHT_A      A on,  B off
├── 15 s   LIGHT_B      A off, B on
├── 15 s   LIGHT_AB     A on,  B on
└── 30 s   POST_STIM    both LEDs off
camera OFF

Running it

Path A — Python simulator (zero installs):

from cuewire.examples import TwoLedThermoSimulator, run_protocol
with TwoLedThermoSimulator() as sim:
    run_protocol(sim.device_path, "two_led_thermo.log")

Path B — real firmware in simavr:

sudo apt install simavr libsimavr-dev
arduino-cli compile --fqbn arduino:avr:uno \
    --output-dir /tmp/two_led_thermo_build \
    examples/two_led_thermo/firmware/two_led_thermo
make -C examples/two_led_thermo/simavr
./examples/two_led_thermo/simavr/simrun \
    /tmp/two_led_thermo_build/two_led_thermo.ino.hex &
python examples/two_led_thermo/run_protocol.py --port /tmp/simavr-uart0

See the full walkthrough in examples/two_led_thermo/README.md.